Over at http://tex.stackexchange.com we've found a few really nice questions and answers centred around a particular package (which happens to be for drawing diagrams in TeX, but that's not relevant). A lot of the resulting answers fall in to the "This should be better known" category so a group of us have decided that we'd like to release a LaTeX package based on that code (see What are your favourite TikZ/PGF answers? if you're interested, though it's not really relevant to this question). At this point, the obvious question is whether we have the right to do this. My question is: can we? And are there any hoops we have to jump through to do it?

Things to take in to consideration:

  1. The standard license for LaTeX packages is the LaTeX Project Public License (see http://www.latex-project.org/lppl/). This is considered as a "free software license" (though not compatible with the GNU GPL, see http://www.gnu.org/licenses/license-list.html#LPPL-1.3a).
  2. The "work" shall be almost completely derived from answers on the site. Of course, they will have to be modified to be mutually compatible and to be more robust, but the intention is that they be based on those answers. (In particular, note that this renders the answers - serious and silly - to I'm worried about Stack Overflow content licensing redundant for this question.)

To refine the questions:

  1. Is what we plan legal?
  2. Who's permission do we need? (Note that there is a difference between what is considerate and what is necessary. Of course, we will ask people but if we get no response, do we need to do more?)
  3. What attribution do we need to put? Clearly, making so that each use of the code puts a footnote in a person's article saying, "This diagram was drawn using code drawn from http://tex.stackexchange.com" would be nice, but kill the package. Scattering it in the code and documentation is only common courtesy, but do we need to do more?

When answering this question, please state your authority! Indeed, I'm hoping that someone from the SE company will stop by and give me the definitive answer - I'm asking in public because I think that that answer will be useful for others to have.

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    As far as I understand it, you will have to follow CC-Wiki's attribution guidelines, and not even SE themselves can absolve you from it - they received the content from each user under that license. I'm fairly sure you have no way of publishing the content under an incompatible license without the express permission from every SO user whose answer(s) you are using... The best way might be creating a CC-Wiki licensed work, and use some workaround to avoid attribution chaos (like, numbering the contributions from 1 to 100, and having a reference list of attributions on a separate page.)
    – Pekka
    Commented Apr 8, 2011 at 7:35
  • ... if separating the attribution from the content in that way is legal under CC-Wiki, which will probably depend on what a LaTeX package looks like.
    – Pekka
    Commented Apr 8, 2011 at 7:43
  • @Pekka: Not being a lawyer, it would seem that we can do what we plan and put in the documentation a page something like "The code in this package was based on the following answers on TeX-SX *list answers with user information*". The LPPL is a free license, so allows modification and distribution. We could pick GNU GPL if that would be a better fit. Commented Apr 8, 2011 at 7:44
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    @Pekka: I guess the correct way for a programmer to think about it is that a LaTeX package is like a module or library and the document like the compiled program. So would the attribution have to be visible in to a user of the compiled program?? Commented Apr 8, 2011 at 7:46
  • @Andrew re GNU GPL, the question there should probably be: "Are the GNU GPL and the LPPL compatible with the 'share alike' clause in CC-Wiki 2.5?" if one of them is compatible (including the restrictions!), you should indeed be able to do this. Re attribution, that is a damn good question. Although I think it's not one Stack Exchange, Inc. can answer, because they are not the creators of the license. Maybe ask CC themselves?
    – Pekka
    Commented Apr 8, 2011 at 7:52
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    Related (but has no definite answer): meta.stackexchange.com/questions/79190/…
    – Pekka
    Commented Apr 8, 2011 at 7:53
  • Interesting question. IANAL but my understanding is that the meaning of a license (or any other legal agreement) is defined by the licence wording as interpreted by a court of law. You need to ask a lawyer. The opinion of CC or SE is not strictly relevant - it doesn't matter what they intended their licence to mean - but of course they may be able to share something they've learned from their own legal advice, and I guess you'll find out what (if anything) would cause them to sue you. You could think of the licence as source code and the courts as a compiler.
    – MarkJ
    Commented Apr 8, 2011 at 8:37
  • Clause 6 of the LPPL seems to be stricter than CC-BY-SA (log of changes, provide access to the original).
    – Caramdir
    Commented Apr 8, 2011 at 20:19

2 Answers 2


CC-BY-SA is incompatible with GNU (see the FSF compatibility list); it might be incompatible with the LPPL, certainly the Creative Commons team haven't been willing to commit themselves on this point. I guess you would need to spend lots more money on lawyers than makes sense to sort this out.

Is this a problem? If the derived content of the package(s) all has the CC-WIKI license, why not use that as the license for the distributed code? For this, you need no permission, only to attribute properly and supply the license as required.

If you do need a proper software license like the GPL or LPPL, you need permission from the original authors. As copyright holders, they can relicense their content under any license they like. Getting this permission from lots of people is often hard work.


Much of the code we plan to publish is written by the three package authors (Caramdir, Andrew Stacey and me) which of course still have the full copyright on it. So publishing that code under LPPL is not a problem at all.

For the other code the permission of the original authors must be received, i.e. the will license it to the package authors under the LPPL. Again, no problem as long they say yes.

The other answers which we do not get permission for (which I find unlikely) can be placed in separate files which are licensed under CC, or even simply rewritten. The copyright is on the code, not on the solution.

In general I'm strongly opposed to publish LaTeX packages under anything else then LPPL, except support scripts which are fine with GPL or another free software license.

  • strongly opposed to publish LaTeX packages under anything else then LPPL - even packages of compiled examples? Commented Apr 8, 2011 at 11:21
  • @Charles: I'm not planning to publish it as examples, but as usable packages. At least my code. Commented Apr 8, 2011 at 11:39
  • This was not clear to me from the threads. OK, I think the solution of having most (if not all) contributions in one LPPL package, and the stragglers in a CC-WIKI package would work well here. Commented Apr 8, 2011 at 12:10

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